The present invention relates to an optical information reading apparatus, more specifically to an apparatus for presentation reading of optical information with removable reader.
In the present description and in the attached claims, the expression “optical information” is used in a broad sense to cover both one-dimensional, stacked and two-dimensional optical codes, wherein information is encoded in the shapes, size, colours and/or mutual positions of elements of at least two distinct colours, and alphanumeric characters, signatures, logos, stamps, trademarks, labels, hand-written text and images in general, and their combinations, in particular present on pre-printed forms, and images containing features suitable for identifying and/or selecting an object based on its shape and/or volume.
In the present description and in the attached claims, the term “light” is used in a broad sense, indicating electromagnetic radiation of a wavelength or a range of wavelengths not just in the visible field, rather also in the ultraviolet and infrared fields. In the same broad sense are terms such as “colour”, “optical”, “image” and “view” used. In particular, the encoded information can be applied onto a substrate in invisible, but sensitive to the ultraviolet or infrared inks.
Imaging reading apparatuses or readers of optical information (of the imager type) are well known. Such readers comprise a photodetector or sensor in the form of an array—linear or preferably matrix-type—of photosensitive elements, capable of generating an electric signal from an optical signal, and typically also image receiving optics, capable of forming an image of the substrate on the sensor—in other words of a three-dimensional or substantially flat object, such as a card or a document—containing the optical information, or a region thereof.
The evolution of the electric signal in space is indicative of the presence or absence, as well as of the relative size and possibly of the colour, of the elements constituting the optical information. Through such an electric signal, suitably processed, it is therefore possible to acquire for example an optical code and decode the information encoded therein.
Also imager readers are within the scope of the invention having the ability to capture photographs or videos and/or the ability to capture images of documents or regions of interest thereof for automatic character recognition or for document handling applications, wherein encoded information is present, also of different types, and not encoded information, in predetermined positions with respect to one another or with respect to the edges of a document or card.
Although readers of optical information of the imager type operating with just ambient light are known, they typically further comprise an illuminator suitable for projecting one or more light beams, possibly variable in intensity or spectral composition, towards the substrate carrying the optical information.
In the present description and in the attached claims, under “illuminator” it is meant to indicate a device having one or more light sources and possible optical components for forming the light beam(s); in the case of a plurality of sources, these can be arranged adjacent to each other or not and can be driven individually, in groups or all together.
An optical information reader of the portable or hand-held type (hand held reader) in general is gun shaped and comprises a reading head equipped with a light input and output window and a grippable handle, possibly equipped with a trigger activation button and with possible other control buttons. An operator holds the reader and “points” it towards an optical code or other optical information to be read, possibly through the help of a visible aiming pattern, starting the reading through a button (“manual” or “attended” reading or “trigger mode”).
The reader houses, suitably located between the head and the handle, the illuminator, the emission and receiving optics, the sensor, as well as possibly one or more rechargeable batteries intended to power the same.
The reader can also house pre-processing electronics of the output signal of the sensor, acquisition and possibly decoding electronics of encoded optical information, recharging circuits of the optional batteries, one or more memories, as well as a communication interface for the transfer of the electric signal emitted by the sensor or of the acquired or decoded optical information, as well as for receiving remote setting and possibly activation controls.
The reader usually has a so-called cradle associated therewith that, besides acting as a support base to hold the reader when not in use, can be used for the collection of the data—raw or already processed—from the reader and their transferal to a remote processor and for the transmission of configuration parameters to the reader. The cradle is for this purpose provided with a communication interface compatible with that of the reader, as well as with a second communication interface with the remote processor. Each communication interface can be via cable, via facing electrical contacts or wireless, using waves, infrared, or optical. It should however be noted that the transferal of data and of the configuration parameters can also take place directly from the reader to the remote processor.
The cradle, powered by the electrical mains, can also act as a recharging base for the reader, through a connection via cable or through facing contacts. Possible transformers and recharging circuits can be housed in the cradle and/or in the reader and/or in a dedicated power supply.
If the cradle allows suitable positioning of the reader, keeping its light input/output window free and pointed towards a predetermined reading zone, the reader can also work without being held and directed by the operator, in a mode called “presentation reader” and the cradle is also called “stand”. An operator or moving system proposes the substrate carrying the optical information in the reading zone, facing the reading window of the reader. In this way, a manual reader is converted into a “fixed” reader, which typically autonomously recognises the presence of the object and does not need a trigger by the operator.
If the reader is powered independently and directly interfaced with the remote processor, the cradle can still be used simply as a support for the “presentation reader” mode. Some readers are configured just to be held and directed by the operator, some just to operate as “presentation reader”, while other can operate in both modes.
The invention in particular concerns this last type of apparatus for presentation reading or presentation reader with removable reader.
US 2008/0191026 A1, on which the preamble of claim 1 is based, discloses such an apparatus, comprising a reader and a stand having a seat for the reader. The reader has an illuminator and the stand has an illuminator. When the reader is housed in the stand, as detected by suitable means, the illuminator of the stand is used, in combination with that of the reader or—when it is more intense than the illuminator of the reader—also by itself, switching off the illuminator of the reader. In this way, a more intense illumination is provided with respect to the trigger mode wherein the reader is held, in order to allow a mode with shorter exposure time and therefore avoid blurred images and provide improved performance.
Starting from such a state of the art, the technical problem at the basis of the invention is to further improve the performance of an apparatus for presentation reading or presentation reader with removable reader in stand mode.
In a first aspect thereof the invention relates to an apparatus for presentation reading with removable reader, comprising an optical information reader and a cradle or stand having a seat for seating the reader facing a predetermined optical information reading zone,
wherein said reader has an illuminator and said stand has an illuminator,
characterised by comprising a processor configured to control a capture of an image of at least one portion of the reading zone, to analyse the image and, based on said analysis, to drive the switching on of either of said illuminator of the reader and/or said illuminator of the stand.
In the present description and in the attached claims, under the expression “drive to switch on” it is meant to also encompass maintaining the switched on state.
The Applicant has recognised that, by dynamically managing the division of the illumination intensity between stand and reader, it is possible to dynamically adapt the illumination of the reading zone to the gloss and/or reflectance characteristics, as determined by the surface finish and/or by the curvature etc. of the object or substrate carrying the optical information, and therefore on each occasion obtain the optimal illumination, also so as to compensate for possible illumination defects of either illuminator. In some cases, it may be advantageous to activate the two illuminators alternatively, in other cases in combination, for example when it is advantageous to illuminate an object from plural angles to reduce reflections.
Preferably, said analysis comprises assessing at least one feature selected from the group consisting of brightness, contrast, presence of a substrate, position of the substrate, presence of optical information of a predetermined type, presence of light spots ascribable to overexposure of a particularly bright or reflective part of the substrate, and presence of illumination unevenness ascribable to a particular slope or shape of the surface of the substrate.
Preferably, said processor also controls, based on such an image analysis, the exposure time of the sensor and/or other reading parameters, such as the gain of the sensor and the portion of the field of view to be captured, activating the acquisition just of a part of the photosensitive elements or pixels of the sensor.
Preferably, the apparatus is further configured for reading optical information of the captured and analysed image or, more preferably, of an image captured after said switch on control.
Preferably, said capturing is preliminary capturing of the image, possibly of a partial and/or subsampled region of the reading zone, to speed up the process and make it compatible with the quick operation typical of stand mode.
Preferably, said apparatus comprises means for detecting the presence of the reader in the stand, and said processor is configured to carry out said analysis and optional preliminary capturing when said means for detecting the presence of the reader in the stand indicate the presence thereof.
Said analysis and optional preliminary capturing can take place continuously (each frame or portion thereof), or periodically at each predetermined time interval, typically of a few milliseconds, or at each predetermined number of images, or at each capturing request for example by a presence sensor of a substrate in the reading zone etc., or also when the apparatus determines that it is needed because the image captured in the normal reading mode is of insufficient quality, as well as in combinations of such circumstances.
Alternatively or in addition, said stand comprises means for detecting the presence of a substrate in the reading zone, and said processor is configured to carry out said analysis and optional preliminary capturing when said means for detecting the presence of a substrate in the reading zone indicate the presence thereof.
Said means for detecting the presence of an object in the reading zone typically comprise a photocell or a battery of photocells, preferably with infrared LEDs so as to be able to be kept constantly switched on without disturbing either the possible operator or the reading of optical information, or an ultrasound detection device.
Preferably, said illuminator of the stand and/or said illuminator of the reader are adjustable intensity illuminators, and said processor is configured to adjust the illumination intensity of said illuminator of the stand and/or of said illuminator of the reader based on said analysis.
In this way it is possible for example to avoid the saturation of the sensor when the object or the substrate is too reflective. It is also possible to avoid the blinding of the sensor by direct reflection of a portion, however small, of the light emitted by the output window and possible components of the stand backwards, towards the sensor, through the receiving optics. Since the typical intensity of the light emitted is a few orders of magnitude greater than the intensity of the light coming from the reading zone and collected by the sensor, even a small increase in the light emitted by the illuminator of the reader, unless suitably screened, can cause spurious reflections on the receiving optics of an intensity such as to prevent reading.
Such adjustment of intensity can comprise the change of the driving current and/or the switching on of just a part of a plurality of light sources of the illuminator, and/or changing the time overlapping between the time interval in which the illumination is active and the time interval in which the integration of photons by the sensor takes place. In turn, such a change of the time overlapping can be adjusted by lengthening/shortening either or both of said time intervals and/or by staggering them by a variable entity.
Preferably, said processor is the main processor of said reader, intended for reading the optical information in the normal reading mode.
In an embodiment said stand comprises an optical component at said illuminator of the reader and/or at an aimer of the reader when housed in the seat, to define an aiming pattern and/or to modify the features of the illuminating beam of the reader, such as angular aperture and radiance profile.
Providing such an optical component represents an invention per se, even independently from providing the double illuminator described above. Such an element, of course, should not extend to the receiving zone, at which, optionally, it is possible to arrange an optically null element, or such as to modify the focal distance of the receiving optics without deteriorating the quality of the image.
Said optical component is advantageously a mask or a transmission hologram. A hologram has the substantial advantage of being able to provide a three-dimensional indication of the reading zone, not just of a base thereof on a plane.
In an embodiment, said optical component is a mask at the aimer of the reader when housed in the seat, defining a two-dimensional aiming pattern.
In an embodiment, said optical component is a mask at the illuminator of the reader when seated in the seat, defining a two-dimensional aiming pattern, with the proviso that the two-dimensional aiming pattern defined by the mask does not interfere with the illuminator function. This can for example be obtained with the fact that the mask defines just the edges (or part of them) of the reading zone or the edges of several regions of interest within the reading zone, or with the fact that the mask blocks just visible wavelengths not used for reading.
In an embodiment, said optical component is a transmission hologram at the aimer of the reader when seated in the seat, advantageously defining a three-dimensional aiming pattern.
In another embodiment, said optical component is a lens, in particular a non-imaging lens with locally defined profile like the one described in EP 1804089 A1, configured to change the radiance profile of the illuminating beam or its shape, or to modify the illuminated field, for example the aperture angle of the beam and/or its angle of incidence on the reading zone.
Said optical component could also be a system of lenses or prisms or even a diffractive optics.
In an embodiment, said stand comprises an aimer.
The use of an aimer on the stand, possibly in addition to an aimer of the reader, which can be used in combination or deactivated in stand mode, allows numerous advantages and represents an invention per se, also independently from providing the double illuminator described above.
First, it is possible to provide a specific aiming pattern most suitable for stand mode. Indeed, while in manual use it is preferable for the user to be given a mainly central indication of the framed field (the edges may not be on the framed object and therefore be lost), which can be done with simple optical components, for stand mode it is advantageous for the peripheral zone to be clearly highlighted, above all for “document handling” applications, which requires more complex and bulky optical components.
Also in the case in which the aiming pattern is the same in trigger mode and in stand mode, it is possible to provide such patterns with different proportions between height and width and/or with the same proportions, but different sizes, without having to use a variable focus aiming optics on the reader.
In cases in which it is foreseen for there to be variability of the conditions of use such as to justify its cost and complexity, it is possible to provide for the aiming/illumination system on the stand to be combined with a variable optical element, such as a mobile optics, or a liquid lens, or a deformable mirror, so as to be able to adapt shape and/or size of the aiming/illumination beam.
In a “document handling” application, the aimer and/or the illuminator of the stand is/are preferably configured to illuminate the predetermined regions of interest and/or the edges thereof, in this way aiding the alignment by the user.
In an embodiment, said aimer of the stand comprises a reflection hologram at the base of the reading zone and an illuminator of said reflection hologram, or a transmission hologram arranged in front of a suitable illuminator. In this way, it is advantageously possible to provide a three-dimensional aiming pattern.
Said aimer of the stand can be integrated in the illuminator of the stand, for example the illuminator of the stand can project an illumination pattern with a very clear visible edge.
Preferably, said stand comprises a loudspeaker and said apparatus comprises a sound indicator or a voice synthesizer configured to supply, through said loudspeaker, indications relating to read optical information and/or indications relating to the positioning of a substrate carrying optical information to be read with respect to the reading zone.
In this way, through the analysis by the processor of the reader of the preliminarily captured image or in the normal reading mode, the apparatus is able to guide the user in the positioning of the object/document, which could be useful also for visually-impaired users, for example in a fixed work station for checking documents.
The sound indicator or voice synthesizer can also indicate, in the case in which the electrical contact is not optimal for recharging, to correctly position the reader in the stand.
Advantageously, the illuminator of the stand comprises at least one light source selected from the group consisting of flash bulbs, laser diodes and LEDs, including high-power LEDs. By exploiting the substantial absence of space, weight and energy consumption constraints of the stand with respect to the reader, it is possible to provide an intense illumination, suitable for stand mode. Short exposure times are possible, avoiding blurred images, even when the speed of passage of the optical information in the reading zone is high and/or the direction of motion is highly variable.
Said illuminator of the stand can comprise light sources drivable according to at least two independent signals, so as to be able to switch on just one or just a few of them. For example, it is possible to provide for light sources forming illumination beams able to be selectively activated that are inclined differently, that are of different intensity, that are of different wavelength(s) (equal to or different from that or those emitted by the illuminator of the reader) etc., and activate such illumination beams for example with alternate flashes.
In this way it is possible to further optimise the performance of the reading apparatus each time using the most suitable illumination, at the discretion of the processor and based on the image analysis.
In an embodiment, said illuminator of the stand and/or said aimer of the stand comprises an array of substantially point sources able to be driven individually to provide an illumination pattern, an aiming pattern and/or an outcome indicating pattern.
Such an array is described for example in document WO 2011/111079 A1, incorporated herein by reference.
Alternatively or in addition, when the illuminator of the stand is orientable, it is also possible for the user to modify the direction of the light beam projected in the reading zone in the most suitable manner for the ambient light conditions, type and orientation of the surface of the object or document, and so on.
Preferably, the stand comprises an accumulation system that stores energy in the periods of low use, and makes it available in the maximum current demand periods, for example a battery but, more preferably, at least one capacitor of the Supercap or Ultracap type.
Preferably, the stand comprises an electrical mains power supply. Such a power supply, possibly in addition to a power supply through USB connection, is not affected by the limits of such USB power sources, which are on the other hand typically limited in current to 500 mA, and which are widely in use as power sources of optical information reading systems.
Advantageously, the stand further comprises an outcome indication device and/or a detector of the presence of an object or substrate in the reading zone and/or a distance or height detector. The latter can for example be a laser measurer of the time-of-flight or phase delay type, or a photocell or array of photocells, or an ultrasound or other type of sensor that is per se known; in this way the stand can generate a signal to drive a receiving autofocus on the reader, if present. Providing said devices in the stand advantageously makes it possible to keep the reader light and lower the consumption of the reader.
Advantageously, the stand has a controller for supplying the reader with a part of a power supply current in input to the stand, preferably in a dynamic manner according to the instantaneous consumption of the stand, so as to save the charge of or to charge a rechargeable battery power supply of the reader.
In a second aspect thereof, the invention relates to a method for optical information presentation reading with an apparatus provided with a removable reader and a cradle or stand, comprising the steps of detecting the presence of a reader in a seat of the stand, facing a predetermined reading zone, carrying out a capture of an image of at least one portion of the reading zone, analysing the image, and based on said analysis driving the switching on of either of an illuminator of the stand and/or an illuminator of the reader.